By virtue of their lubricating mechanism, which renders them independent of an extraneous pressurized oil source, radial sliding bearings of this construction are particularly suitable for supporting shafts with high vertical loads, where any failure of the pressurized oil supply will very quickly lead to the destruction of the bearing contact surfaces and journals. The mechanism of the lubricating effect according to the present invention ensures the formation of a hydrodynamically generated lubricating oil wedge between the sliding surfaces during the entire time when the shaft is in rotation, from the start through the steady service state to stoppage. Seizing of the bearing and the shaft, such as can occur in the case of a brief failure of a pressurized oil supply, is therefore virtually excluded.
Known radial sliding bearings have loose lubricating rings, or rings connected firmly to the shaft or integral with the latter, to transport the lubricating oil from the lubricating oil sump to the points where the lubricating oil wedge is required to be formed. They dip into the lubricating oil sump, the level of which is placed below the outlet aperture for the shaft from the bearing housing in order to prevent lubricating oil losses, and entrain the oil upwards, after which the oil passes into the bearing gaps.
However, the field of application of such bearing constructions is restricted to cases where the heating of the oil is not so great that an oil cooler is required, or at worst an oil cooler in the sump is sufficient, but the cooling action of such oil coolers is generally deficient. This means that the means referred to for the self-transport of the lubricating oil to the bearing points are only satisfactory up to certain shaft diameters and circumferential speeds of the journal, for which the oil heating the oil foam formation remain within admissible limits. This is generally the case for shaft diameters below 600 mm and journal circumference speeds up to a maximum of 20 m/s.
More heavily loaded horizontal sliding bearings would run inadmissibly hot without oil coolers provided outside the housing. Such bearings are customarily equipped with a pump to circulate the lubricating oil through the bearing and the oil cooler or coolers. In order to prevent bearing damage, these elements (that is to say the pumps and coolers) must have backups (that is to say, they must be present at least in duplicate). Self-contained operation of such highly loaded bearings, without extraneous energy sources, is therefore impossible.
The problem outlined above also represents a considerable factor for highly axially loaded end-thrust sliding bearings of hydroelectric generators, for example. In this case if the bearing ran hot due to a failure of the lubricating oil pump, this would involve not only high repair costs, but also the failure of the power supply for a long time, with significant consequent economic losses.
The problem has been solved for such axial sliding bearings by a self-pumping hydrodynamic plain bearing proposed in Swiss Pat. No. 651,362 (namely for the guide bearing of an end-thrust sliding bearing). The guide bearing absorbs the horizontal forces acting upon the journal, and like the axial bearing itself, the journal is composed of individual segments. The oil-transporting elements of this guide bearing consist of recesses in the entry regions of the segments, as viewed in the direction of the shaft circumferential speed. These recesses extend with constant radial depth over a part of their length and taper in wedge shape after a step in the final part in the running direction, whereby the oil is drawn into the lubricating gap there and forms the hydrodynamic lubricating film in the remaining part of the running surface of the bearing segment. Because more oil is entrained out of the oil sump by the shaft due to the viscosity in the initial deeper part of the recess than is necessary to form the lubricating film and can be absorbed by the lubricating film gap, a lubricant discharge duct is provided extending transversely to the running direction in front of the said step. The excess lubricant stream is discharged through the lubricant discharge duct back into the oil sump under pressure which has built up in front of the wedge-shaped taper, or else, if larger quantities of heat have to be dissipated, the excess lubricant stream is forced through an external cooler and transported back into the sump. This part of the lubricant stream constitutes the transport quantity circulated by the viscosity; the far smaller residue is squeezed through the lubricating film gap and leaves the latter heated at the end of the bearing segment. The circulation of the lubricant on this principle is therefore independent on any pump devices and therefore satisfies the initial desideratum of absolute reliability of the oil supply and oil cooling.
However, the principle of the above-described form is not suitable for radial sliding bearings with a horizontal position of the shaft. On the contrary, it requires certain modifications for this purpose, which form the object of the present invention.